As currently performed, open surgical biopsy of suspected breast cancer is guided by a flexible hook-wire which is embedded into the cancer by means of radiologic (mammographic or ultrasound) imaging. The surgeon makes an incision into the breast, finds the area of tissue where the hook-wire is embedded, and removes it as a biopsy specimen. Because the surgeon can not see the tip of the embedded hook-wire (it is considered undesirable to cut through the suspected cancer) and also because the hook-wire is a flimsy anchor which can be easily dislodged from its position within the breast, removal of the biopsy specimen involves some guess work which results in a degree of inaccuracy and imprecision. Suspected cancers are often incompletely excised, and occasionally are missed altogether.
With Coaxial Biopsy as described in patent application Ser. No. 08/386,111, a rigid rod is inserted through the suspected cancer with guidance provided by radiologic imaging. The rigid rod is a K-wire, a common surgical tool, which may have a diameter three to six times greater than the standard flexible hook-wire used for needle localization of non-palpable breast masses prior to open surgical excision. The rod establishes a mechanical guide over which the biopsy device is advanced, like a train rolling down a rail, and stabilizes the cancer in the path of the cutting instrument so that it will be removed by the biopsy process.
The concept of rigidity of the rod is central to Coaxial Biopsy as described in the parent application. While a flexible hook-wire may indicate the location of the suspected cancer, one skilled in the art would know that a hook-wire can not provide mechanical guidance for the cutting tool, nor can it stabilize the cancer in the path of the cutting device. The difference between hook-wire guided biopsy and Coaxial Biopsy is perhaps best understood by analogy: one can catch fish with a hook on the end of a flexible fishing line, or one can spear the fish with a barbed harpoon on a long handle. Both systems are superficially similar in that they hook into the fish at some point, but one is flexible and the other is rigid. The cutting device (the cannula) is concentrically positioned along the rod; the rod guides the cannula to the cancer.
What has been disclosed previously in the parent application is a method of marking the location of a suspected cancer so it can be identified with radiologic imaging (either by x-ray fluoroscopy or by ultrasound); normally the cancer is not clearly visible except by mammographic imaging. A metal target implanted into the immediate vicinity of the suspected cancer can be seen by fluoroscopy or ultrasound. The advance of a scalpel blade cutting a path down the rod to a point just proximal to the metal target and the progress of the cannula as it slides over the rod and incises the specimen containing the target are monitored radiologically, eliminating the guess work associated with standard hook-wire guided biopsy. This method is advantageous compared with stereotactically-guided biopsy because it can be performed without the need for a special stereotactic x-ray table. All that is required is a mammography machine for placement of the rod and the target, and an ultrasound or fluoroscopic machine for monitoring the biopsy in the operating room. While this is preferable to stereotactic biopsy and standard surgical biopsy with hook-wire guidance, the requirement for an operative ultrasound or fluoroscopic machine is a relative disadvantage, since not all surgeons are familiar with fluoroscopic or ultrasound imaging.
Also disclosed previously are cutting cannulae with internal snare mechanisms. However, these require at least two concentrically positioned cannulae to maintain the snare wire between them; the inner cannula in these prior patents is then withdrawn to reveal the snare wire, which is then tightened to amputate the specimen. These internal-snare devices require multiple moving parts, and share the disadvantage of complexity associated therewith.
The snare previously disclosed as part of the Coaxial Biopsy system is an external snare slipped over the outside of the cannula by a modification of an existing tonsil-snare device. While this works effectively, it requires an initial relaxing incision to be made along the cannula to pass the device through, and it is a separate tool. If a simpler internal snare mechanism could be devised, this would incorporate two tools into one by combining the cannula and the snare device.
Examples of prior art surgical apparati and procedures for performing biopsies can be found in U.S. Pat. No. 5,353,804 for Method and Device for Percutaneous Excisional Breast Biopsy issued Oct. 11, 1994 to Kornberg, et al and U.S. Pat. No. 5,133,360 for Spears Retriever issued Jul. 28, 1992 to Colin P. Spears and in the prior art cited these patents.
It will be appreciated that there exists a continuing need for improvement in breast biopsy which is partially satisfied by the Coaxial Biopsy system disclosed in the parent application. However, additional improvements of Coaxial Biopsy to enable intra-operative location of the suspected cancer without additional fluoroscopic or ultrasound imaging, and amputation of the specimen by an improved internal snare mechanism would be useful. Also, a method of injecting a metal clip into the breast to mark the location of the biopsy would be helpful in case further therapy such as wider surgical excision is needed. Finally, a stabilization device to position the breast most conveniently during Coaxial biopsy would be useful.